I have been transfering images from the Avery and HP iron on paper. I am practicing with small project of shirts for my daughter before I buy a heat press etc and I dont want to pay a screen printer for screens etc just to do small projects. When I iron on the image with this paper is left a yellow sqaure around the image the same size as the paper.

It put the image on just fine but then it was all yellow. What am I doing wrong? Where do you buy
jpss paper? Is it better? MAybe my iron isnt hot enough?? Let me know what you think. Thanks!